Equity Method Investments - Summary of Equity Method Investment Financial Information (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020		Mar. 31, 2019		Dec. 31, 2019
Schedule of Equity Method Investments [Line Items]
Equity method investments		$ 3,992				$ 5,275
Revenues and other income		120		$ 546	[1]
Costs and expenses		236		275	[1]
Income (loss) from operations		(116)		271	[1]
Net income (loss)		(151)		252	[1]
Income/(loss) from equity method investments(2)		(1,184)	[2],[3],[4]	77	[1],[5],[6],[7]
Current assets		645				864
Noncurrent assets		10,499				10,996
Current liabilities		348				437
Noncurrent liabilities		1,403				1,127
Equity Method Investment, Other than Temporary Impairment		$ 1,264
MarEn Bakken Company LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		25.00%
Illinois Extension
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		35.00%
LOOP
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		41.00%
Whistler Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		38.00%
W2W Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		50.00%
Wink to Webster Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		15.00%
Explorer
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		25.00%
MarkWest Utica EMG
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		57.00%
Equity Method Investment, Other than Temporary Impairment		$ 1,251
Sherwood Midstream
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		50.00%
Jefferson Dry Gas
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		67.00%
Centrahoma Processing LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		40.00%
Other VIEs [Member]
Schedule of Equity Method Investments [Line Items]
Revenues and other income		$ (217)		155	[1]
Costs and expenses		104		77	[1]
Income (loss) from operations		(321)		78	[1]
Net income (loss)		(337)		71	[1]
Income/(loss) from equity method investments(2)		(1,222)	[4]	27	[1]
Current assets		320				534
Noncurrent assets		5,384				5,862
Current liabilities		153				192
Noncurrent liabilities		544				305
Non-VIEs [Member]
Schedule of Equity Method Investments [Line Items]
Revenues and other income		337		391	[1]
Costs and expenses		132		198	[1]
Income (loss) from operations		205		193	[1]
Net income (loss)		186		181	[1]
Income/(loss) from equity method investments(2)		38		50	[1]
Current assets		325				330
Noncurrent assets		5,115				5,134
Current liabilities		195				245
Noncurrent liabilities		$ 859				822
Indirect Ownership Interest [Member] | Sherwood Midstream Holdings
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		24.10%
Direct Ownership Interest [Member] | Andeavor Logistics Rio Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		67.00%
Direct Ownership Interest [Member] | Minnesota Pipe Line Company, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		17.00%
Direct Ownership Interest [Member] | Rendezvous Gas Services, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		78.00%
Direct Ownership Interest [Member] | Sherwood Midstream Holdings
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage		52.00%
G&P
Schedule of Equity Method Investments [Line Items]
Difference between carrying amount and underlying equity		$ (60)				1,000
Difference between carrying amount and underlying equity portion related to goodwill		31				498
G&P | MarkWest Utica EMG
Schedule of Equity Method Investments [Line Items]
Equity method investments	[8]	712				1,984
G&P | Sherwood Midstream
Schedule of Equity Method Investments [Line Items]
Equity method investments	[8]	546				537
G&P | Jefferson Dry Gas
Schedule of Equity Method Investments [Line Items]
Equity method investments	[8]	302				302
G&P | Rendezvous Gas Services, L.L.C. [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	[8]	167				170
G&P | Sherwood Midstream Holdings
Schedule of Equity Method Investments [Line Items]
Equity method investments	[8]	155				157
G&P | Centrahoma Processing LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments		150				153
G&P | Other VIEs and Non-VIEs [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	[8]	206				198
L&S
Schedule of Equity Method Investments [Line Items]
Difference between carrying amount and underlying equity		330				329
Difference between carrying amount and underlying equity portion related to goodwill		167				167
L&S | MarEn Bakken Company LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments		479				481
L&S | Illinois Extension
Schedule of Equity Method Investments [Line Items]
Equity method investments		271				265
L&S | LOOP
Schedule of Equity Method Investments [Line Items]
Equity method investments		239				238
L&S | Andeavor Logistics Rio Pipeline [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	[8]	200				202
L&S | Minnesota Pipe Line Company, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments		190				190
L&S | Whistler Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	[8]	163				134
L&S | W2W Holdings LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	[8],[9]	76				0
L&S | Wink to Webster Pipeline LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	[8],[9]	0				126
L&S | Explorer
Schedule of Equity Method Investments [Line Items]
Equity method investments		81				83
L&S | Other VIEs and Non-VIEs [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investments	[8]	55				55
Operating Segments | G&P
Schedule of Equity Method Investments [Line Items]
Equity method investments		2,238				3,501
Income/(loss) from equity method investments(2)		(1,234)		32	[7]
Operating Segments | L&S
Schedule of Equity Method Investments [Line Items]
Equity method investments		1,754				$ 1,774
Income/(loss) from equity method investments(2)		$ 50		$ 45	[7]

[1] Financial information for the first quarter of 2019 has been retrospectively adjusted for the acquisition of ANDX. See Notes 1 and 3.

[2] The 2020 period includes $1,264 million of impairment expense. See Note 4.

[3] The 2020 period includes $1,264 million of impairment expense. See Note 4.

[4] Includes the impact of any basis differential amortization or accretion in addition to the impairment of $1,264 million.

[5] Financial information for the first quarter of 2019 has been retrospectively adjusted for the acquisition of ANDX. See Notes 1 and 3.

[6] Financial information for the first quarter of 2019 has been retrospectively adjusted for the acquisition of ANDX. See Notes 1 and 3.

[7] Financial information for the first quarter of 2019 has been retrospectively adjusted for the acquisition of ANDX. See Notes 1 and 3.

[8] Investments deemed to be VIE’s. Some investments included within “Other” have also been deemed to be VIE’s.

[9] During the three months ended March 31, 2020, we contributed our ownership in Wink to Webster Pipeline LLC to W2W Holdings LLC.